There is increasing evidence of the health risks of various exposures during pregnancy for offspring. One of the most well-recognised of such risks is alcohol use. Some bioethicists argue that women who drink excessive amounts of alcohol during pregnancy ought to be considered morally – and even legally – responsible for any resulting harms to their children. Social norms around pregnancy reflect this: pregnant women who drink alcohol often face moral disapproval and even condemnation from others. Yet, such arguments fail to acknowledge the role of structural inequality and other social determinants which contribute to drinking behaviours among pregnant women - in other words, how pregnant women themselves are vulnerable. In this talk, I introduce the concept of vulnerability in order to make sense of the moral responsibility of women who drink excessive alcohol during pregnancy. Drawing on bioethical theories of vulnerability, I argue that the concept of vulnerability can be used to better understand a) the degree of autonomy of women at risk of heavy alcohol use during pregnancy, and b) the increased risk of personal harm such women may face in moderating their alcohol use. I argue that social attitudes towards pregnant women - and policy and legal debates on foetal alcohol spectrum disorder - need to account for the relative vulnerability of pregnant women in positions of structural disadvantage.